JP 3455730 B discloses electronic equipment comprising connecting means for connecting an extended unit for functional extension; instructing means for instructing to power the extended unit; and powering control means for starting powering the extended unit while keeping a main power source in the electronic equipment body off when instructed by the instructing mean to power the extended unit under a situation where the main power source in the electronic equipment body is in its off state. According to this technique, in a situation where only the function of the extended unit is desired, only the extended unit is powered. Thus, it is possible to reduce power consumption of the electronic equipment when compared with a configuration in which the electronic equipment as a whole is powered even in such a situation.
Recently, due to rapid evolution speed of the multimedia apparatus of vehicles, an extended life of the vehicle itself, etc., such a configuration of the multimedia apparatus to which an extension device can be retrofitted to the existing multimedia apparatus so as to enable increasing functionality of the existing multimedia apparatus is proposed. The electronic equipment disclosed in JP 3455730 B also has a configuration of its kind.
There are ways of increasing functionality of the existing multimedia apparatus by connecting the extension device; one way is to add a new function which does not exist in the existing multimedia apparatus by using the extension device, and another way is to increase functionality of a particular function which exists in the existing multimedia apparatus by using the extension device. According to the latter way, when the extension device is connected, then the functional module of the extension device replaces a corresponding existing functional module in the existing multimedia apparatus. This may lead to a situation where the existing functional module may not be substantially used. Even in such a situation, the existing functional module consumes electric power as standby power, etc. This is not desirable in terms of power saving.